The present invention relates to a method and apparatus for manufacturing ceramic articles. More particularly, this invention relates to an improved method and apparatus for vacuum forming, compressing, heating, and extruding ceramic articles of manufacture.
The ceramics manufacturing industry has long sought to develop more efficient and economical methods and apparatus for the manufacture of ceramic articles from ceramic components such as ceramic particles or powders, clay, etc. Examples of prior art in the field include the following U.S. Patents:
Many ceramic articles are produced by forming the articles from a wet plastic clay and then slowly heating the formed clay articles for hours or days. This process is cumbersome, time consuming, and costly.
The heating, or sintering, step involves the welding together and growth of contact area between two or more initially distinct particles at elevated temperatures (typically above one-half of, yet below, the melting point). It has long been known that sintering of ceramic powders is enhanced by compressing or compacting the ceramic powder. Compacting is generally done at room temperature, and the resulting compacted powder is subsequently sintered at elevated temperatures.
For example, the patent to Fiorentino teaches the production of billet and extruded products from particulate materials such as ceramics. In the Fiorentino patent, a method and apparatus is disclosed for consolidating particulate materials in press equipment utilizing a reusable canister sealed in a vacuum from the atmosphere and heated in the press equipment at elevated temperatures and pressures.
Use of such canisters, however, is expensive, time consuming, and labor intensive. The canister must be packed with ceramic powder, sealed and usually pressed in a vacuum, placed in an oven or furnace, then heated, and then opened to remove the article. The process thus requires a variety of steps that are labor intensive or require substantial automation equipment. The process is also time consuming.
Other prior art processes have been developed in order to compact or press the ceramic powders at elevated temperatures and therefore simultaneously press and heat the powder. See, e.g., McGraw-Hill, Encyclopedia of Science and Technology, pp.1764-65 (4th Ed. 1998). Typically, however, these prior art hot pressing processes utilize an expensive, bulky vacuum housing or chamber containing the oven or furnace and pressing apparatus.
Another problem with such prior art processes is that they typically do not achieve the level of vitrification (glass bonding) of materials in the ceramic article being manufactured, particularly at the outer surface of the ceramic article being manufactured where enhanced vitrification is most desirable. Attaining such vitrification with the prior art methods such as hot pressing thus typically would require additional or extended heating of the article being hot pressed, which not only involves additional time and processing steps but also can conflict with the amount of time desired to attain the desired overall ceramic article properties achieved by the basic sintering process that takes place in the entire heating process.
The other prior art listed above but not specifically described further catalog the prior art of which the applicant is aware. These references diverge even more starkly from the references specifically distinguished above.
The applicant has invented an apparatus and method forming ceramic articles from ceramic components, preferably ceramic powders. The method includes the following steps with the following apparatus: depositing ceramic components into a forming chamber mounted within a heating chamber; drawing a vacuum within and heating the forming chamber; opening an extrusion end of the ceramic forming chamber; and extruding the fused ceramic article through the extrusion end of the forming chamber.
Preferably, the method also includes pressing the ceramic components during the vacuum drawing and heating step. In addition, the heating chamber preferably continues to heat the forming chamber and its extrusion end during the extrusion step.
In a preferred embodiment, the vacuum is drawn by a vacuum chamber mounted within the heating chamber to surround the forming chamber. Also, the pressing step is preferably performed with a press mounted within a contractible bellows section of the vacuum chamber, and preferably the press is slidable within the forming chamber.
In a particularly preferred embodiment, the extrusion end of the forming chamber has a configuration and is heated sufficiently so that the periphery of the ceramic article is compressed and/or vitrified and/or further vitrified by the interaction of the ceramic article passing through the heated extrusion end. Most preferably, the forming chamber is not removed from the heating or vacuum chambers during the entire process.
There are other aspects and alternative or preferred embodiments of the invention. They will become apparent as the specification proceeds.
Accordingly, a primary object of the present invention is to provide a new and novel method and apparatus for hot vacuum extrusion of ceramics.
A further object of the present invention is to provide a device as characterized above which lends itself to mass production techniques.
Viewed from a first vantage point it is an object of the present invention to provide an apparatus for extrusion manufacturing ceramic articles from ceramic component materials, the a apparatus comprising in combination: a heating element; a vacuum chamber having an openable sealing member and being mounted adjacent the heating element whereby the heating element may heat the vacuum chamber; a ceramic forming chamber mounted adjacent the heat chamber and within the vacuum chamber, the ceramic forming chamber having an extrusion member; and a ceramic press movably penetrating ceramic extrusion chamber whereby ceramic component materials may be heated and pressed within the ceramic forming chamber and extruded out of the ceramic extrusion chamber through the extrusion member and the openable sealing member in the vacuum chamber.
Viewed from a second vantage point it is an object of the present invention to provide an apparatus for extrusion manufacturing ceramic articles from particulate ceramic components, the apparatus comprising in combination: a heating chamber; a vacuum chamber having being mounted within the heating chamber whereby the heating chamber may surround and heat a substantial portion of the vacuum chamber; a ceramic forming chamber having a press end opposite an extrusion end and an axial length spanning between the press end and the extrusion end, the ceramic extrusion chamber being mounted within and enclosed by the vacuum chamber so that the axial length of the ceramic forming chamber is surrounded by the heating element; and a ceramic press slidably penetrating the press end of the ceramic forming chamber whereby the particulate ceramic components may be heated and fused within the confines of the ceramic forming chamber and, after opening of the extrusion end of the ceramic forming chamber, extruded out of the ceramic forming chamber through the extrusion end and the vacuum chamber.
Viewed from a third vantage point it is an object of the present invention to provide a method of forming and extruding ceramic articles from ceramic component materials, the method comprising the steps of: depositing ceramic component materials in a ceramic forming chamber within a heating chamber; heating the ceramic forming chamber with the heating chamber and drawing a vacuum within the ceramic forming chamber in order to fuse and form the ceramic components materials; opening an extrusion end of the ceramic forming chamber without removing the ceramic forming chamber from the heating chamber; and extruding the fused and formed ceramic component materials through the extrusion end of the forming chamber.
Viewed from a fourth vantage point it is an object of the present invention to provide a method of heating, pressing, forming, and extruding ceramic articles of manufacture from ceramic components, the method comprising the steps of: depositing ceramic components into a forming chamber fixedly mounted within a vacuum chamber; drawing a vacuum within the vacuum chamber; pressing the ceramic components with a press slidably penetrating the forming chamber, and heating the vacuum chamber, the forming chamber, and the ceramic components with a heater assembly mounted externally to the vacuum chamber, whereby the ceramic components become fused within the forming chamber into a ceramic article; opening an extrusion end of the ceramic forming chamber while the forming chamber remains fixedly mounted within the vacuum chamber; extruding the fused ceramic article from the vacuum chamber by pressing the ceramic article with the sidable press so that the ceramic article extrudes through the extrusion end of the ceramic forming chamber.
These and other objects will be made manifest when considering the following detailed specification when taken in conjunction with the appended drawing figures. It is to be understood that the scope of the invention is to be determined by the claims and not by whether any given subject matter achieves all objects stated herein.